* {
  margin : 0;
  padding : 0;
  box-sizing: border-box;
  font-family: "微软雅黑",sans-serif;
}

// BFC解决父元素塌陷和margin复用问题
@mixin cf($className:cf){
  #{$className}:before,
  #{$className}:after {
    content: " ";
    display: table;
  }
  #{$className}:after {
    clear: both;
  }
  #{$className} {
    *zoom: 1;
  }
}